Cancer begins in the cells of the patient and forms malignant tumors that are often treated by surgical resection. Such surgical treatments attempt to remove as much of a tumor as possible, but cancerous cells infiltrate into the tissue adjacent the tumor such that there is no clear boundary. Also, certain procedures seek to limit the treatment margin around the tumor to reduce the amount of healthy tissue removed from the patient. In breast cancer, for example, patients prefer to limit the size of the lumpectomy resection to avoid excessive reduction or non-uniformities of the breast. Both of these factors limit the efficacy of surgical procedures for treating cancer. As such, radiation therapy has become a significant and highly successful process for treating breast cancer, lung cancer, brain cancer and many other types of localized cancers. Radiation therapy is particularly useful for treating (a) tissue after resecting a tumor, (b) centrally located tumors, and/or (c) small cell tumors that cannot be surgically resected. Radiation therapy can also be used as a palliative treatment when a cure is not possible.
Breast cancer has recently been treated by surgically resecting cancerous breast tissue and subsequently treating the remaining tissue surrounding the resection cavity using radiation. Proxima Corporation and Xoft, Inc. have developed breast brachytherapy devices and systems for selectively irradiating the portion of the tissue surrounding the resection cavity created by a lumpectomy. The existing breast brachytherapy devices have a balloon configured to be implanted in the cavity within the breast and an internal radiation source that can be placed within the balloon. After performing a lumpectomy, the balloon is inserted into the surgical cavity and inflated until the balloon presses against the tissue. The balloon is typically left in the patient for approximately five days over which two radiation treatments per day are performed. Each radiation treatment includes inserting the radiation source into the balloon and activating the radiation source to deliver ionizing radiation for approximately 10-15 minutes. After all of the radiation treatments have been performed during the multi-day course of treatment, the balloon is deflated and removed from the patient.
Breast brachytherapy procedures, however, can be challenging. For example, it may be difficult to determine whether the balloon has been inflated accurately and to monitor the balloon to ensure that the balloon has maintained the desired size throughout the multi-day course of treatment. The size of the balloon is currently determined by instilling radiopaque contrast into the balloon and measuring a resulting CT or X-ray image using a ruler. The patient must accordingly undergo a CT scan or another type of X-ray to obtain the image, and then a practitioner must evaluate the image to determine if the balloon is at the desired size. This is time-consuming and expensive, and it should be performed each day during the course of treatment. This process also exposes the patient to additional radiation.
Breast brachytherapy may also have disadvantages associated with using an internal radiation source. For example, the balloon may move within the lumpectomy cavity over the course of treatment, which can cause the internal radiation source to over irradiate some areas and under irradiate other areas. Many existing systems do not detect the relative position between the balloon and the breast to mitigate this problem. Moreover, when the radiation source is asymmetrically positioned within the balloon (e.g., spaced apart from a rotational center line of the balloon), the rotational orientation of the balloon within the lumpectomy cavity can cause the radiation source to be located at an undesirable position relative to the tissue. Conventional techniques also do not identify the rotational orientation of the balloon. This can be problematic because the balloon can move after it has been implanted over the course of treatment, or the balloon may not inflate as planned. Conventional breast brachytherapy systems are also relatively large because they must contain both a balloon and an internal radiation source. Many patients are not comfortable with having a radiation source within their body or with having a large catheter projecting from their body for a number of days, and therefore a sizable number of patients elect not to undergo breast brachytherapy.
In light of the challenges associated with breast brachytherapy procedures, partial breast irradiation using an external radiation beam has been proposed. Although radiation beams, such as Three-Dimensional Conformal Radiation Therapy beams, can shape radiation beams to conform to the target tissue, it is still difficult to use external beam radiation to treat the tissue around the resection cavities in many applications. For example, the size and shape of the cavity may change over the multi-day period typically required for external beam radiation treatments, or the treatment target may move during the treatment sessions. As such, there is a need for improving external beam radiation for partial breast irradiation and other procedures that seek to irradiate controlled treatment margins around resection cavities.